Premium Membership ♕

Save 50% on all EEP Academy courses with Enterprise Membership Plan and study specialized LV/MV/HV technical articles & guides.

Home / Technical Articles / Capacitive Voltage Transformers (CVT) For HV Measurements

66 kV and upwards

Capacitive voltage transformers (CVTs) are used on higher voltage levels, starting from 66 kV and upwards. The type of the CVT is always a single-pole one, thus the connection is between phase and earth. The higher the voltage level is, the more price-competitive the capacitive type becomes.

HV Capacitive Voltage Transformers
HV Capacitive Voltage Transformers (photo credit:

One of the advantages the capacitive type has, in comparison to the inductive type, is the possibility to use capacitive voltage transformers as high-frequency coupling units towards the primary system (over headlines).

A typical application would be to utilize the CVTs for power line carrier (PLC) high-frequency signal interface units. For the voltage measurement purposes, the behavior and the data specification of CVTs follow the same guide lines as the inductive ones.

In addition, the possibility for high-frequency signal coupling calls for a specified value for rated capacitance (Cn).

This value is chosen considering the following issues //

  • Voltage magnitude to be measured
  • Demands from PLC system (frequency, bandwidth, connections)
  • Capacitive voltage transformer manufacturing considerations

The construction of capacitive voltage transformers

The figure above shows the principle of a capacitive voltage divider on which the capacitive voltage transformer is based. The trimming windings are used for fine tuning the output signal to correspond with the required accuracy class requirements. The compensating reactor compensates the phase angle shift caused by the capacitive voltage divider.

Capacitive voltage transformer’s principal construction
Figure 1 – Capacitive voltage transformer’s principal construction

All capacitive voltage transformers require some sort of ferroresonance damping circuit.

The capacitance in the voltage divider, in series with the inductance of the compensating reactor and the wound transformer (inside the electromagnetic unit EMU), constitutes a tuned resonance circuit. Unlike with the inductive type of voltage transformers, the CVTs usually have the ferroresonance damping circuit inbuilt in the CVT itself, as shown in the previous figure.

Capacitor voltage transformer (CVT) nameplate
Capacitor voltage transformer (CVT) nameplate (photo credit:

At higher system voltages, the resonance phenomenon usually takes place on fundamental or on sub-harmonic frequencies, resulting in voltage transformer heating (finally damages) and non-selective operations of protective relaying possible protective relaying non-selective operations.

The modern CVTs are utilizing the so-called “adaptive” damping circuits.

The circuit consists of a saturable series reactor and a loading resistor. This circuit is connected in parallel to one of the secondary cores. During ferroresonance conditions, high voltages appear, saturating the reactor and turning the damping resistor on to effectively mitigate the parasitic voltage. During normal system conditions, the reactor presents high reactance, effectively “switching off” the damping resistor.

Possible triggering factors for the ferroresonance phenomena could be //

  • Planned primary switchings in the system
  • Circuit breaker trippings caused by primary fault
  • High-speed autoreclosing
Capacitive Voltage Transformers (CVT)
Capacitive Voltage Transformers (photo credit:

Reference // ABB’s Distribution Automation Handbook

Premium Membership

Get access to premium HV/MV/LV technical articles, electrical engineering guides, research studies and much more! It helps you to shape up your technical skills in your everyday life as an electrical engineer.
More Information

Edvard Csanyi

Electrical engineer, programmer and founder of EEP. Highly specialized for design of LV/MV switchgears and LV high power busbar trunking (<6300A) in power substations, commercial buildings and industry facilities. Professional in AutoCAD programming.


  1. Ànas Siddiqui
    Oct 05, 2022

    Can you advise please, During erection of 220 kv Capacitive Voltage transformer, we should connect the CVT and Coupling Capacitor,
    Shall we remove pressure release valve cap before connecting both unit together Or we should keep pressure release valve as it is and coupled bothe unit by nuts and bolts that it.

    Kindly guide me.

  2. jaya deepika
    Nov 02, 2019

    as an diploma junior engineer what i’ve to learn

  3. Arturo Carcido
    Aug 27, 2019

    I am looking to get a bit more educated on the application and maintenance testing requirements for these CVT’s. Also, recommended Commissioning test requirements.

  4. ehsan bakhshizadeh
    Dec 10, 2017

    Dear Sir,
    I have a question about CVT. In a 400kv high voltage substation with one & half breaker system, there are 4 CVTs for BB1,BB2,Node1, Node2 and 3 circuit breaker Q01,Q02,Q03. For closing of CBs there is one protection relay 6MD664 for synchronization that has one 3 phase analogue voltage input(V1,V2,V3,VN) and one single(V4) phase. Question: can apply 3 independent CVTs to 3 phase analogue voltage input(V1,V2,V3,VN)?if so , the 4th cvt will be applied to V4 input of relay.

  5. DineshKumar
    Dec 04, 2017

    This is Dhinesh, just telme how to calculate the magnetizing reactance value of EMU Unit? And then primary and secondary impedance of EMU Unit?? There’s any formula for that means telme as soon as possible!!!!

    Oct 22, 2017

    Very educative article on Capacitive Voltage Transformers otherwise what could be the life time of these transformers?

  7. scott
    Dec 09, 2016

    If a name plate value of a capacitor is C1=9800, and C2= 78000, what is the effect of larger capacitances for either one of these capacitors? Is it solely an effect on the divider, or will an error happen on the step relaying function?

  8. Steven Xu
    Jun 02, 2016

    Now we design out High voltage Screw Ceramic Capacitor,

    500PF 24KVAC, ø25x44mm
    Withstand Voltage 50KVAC
    Lightning impulse up to 120KVAC

    This capacitor is important components of capacitive coupler.

    Datasheet can be send on request.

  9. ajay vikrant
    Dec 27, 2015

    Dear Sir,

    Now, Coupling capacitor of CVT in EHV system are not of any use as State Power Utilities are preferring OPGW cable for communication and lightning protection of transmission line, therefore, now we should go for VT instead of CVT or not as function of Voltage Transformers now end with protection and metering. What are the demerits if we prefer VT instead of CVT at line terminating point. Also clarify whether CVTs are costly than Vts or not.

    Requesting for an early reply.

Leave a Comment

Tell us what you're thinking. We care about your opinion! Please keep in mind that comments are moderated and rel="nofollow" is in use. So, please do not use a spammy keyword or a domain as your name, or it will be deleted. Let's have a professional and meaningful conversation instead. Thanks for dropping by!

5  ×  six  =  

Learn How to Design Power Systems

Learn to design LV/MV/HV power systems through professional video courses. Lifetime access. Enjoy learning!

Subscribe to Weekly Newsletter

Subscribe to our Weekly Digest newsletter and receive free updates on new technical articles, video courses and guides (PDF).
EEP Academy Courses - A hand crafted cutting-edge electrical engineering knowledge